/*
 * Copyright 2017 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
#ifndef SkShadowUtils_DEFINED
#define SkShadowUtils_DEFINED

#include "include/core/SkColor.h"
#include "include/core/SkScalar.h"
#include "include/core/SkTypes.h"

#include <cstdint>

class SkCanvas;
class SkMatrix;
class SkPath;
struct SkPoint3;
struct SkRect;

enum SkShadowFlags {
    kNone_ShadowFlag = 0x00,
    /* * The occluding object is not opaque. Knowing that the occluder is opaque allows
     * us to cull shadow geometry behind it and improve performance. */
    kTransparentOccluder_ShadowFlag = 0x01,
    /* * Don't try to use analytic shadows. */
    kGeometricOnly_ShadowFlag = 0x02,
    /* * Light position represents a direction, light radius is blur radius at elevation 1 */
    kDirectionalLight_ShadowFlag = 0x04,
    /* * Concave paths will only use blur to generate the shadow */
    kConcaveBlurOnly_ShadowFlag = 0x08,
    /* * mask for all shadow flags */
    kAll_ShadowFlag = 0x0F
};

class SK_API SkShadowUtils {
public:
    /* *
     * Draw an offset spot shadow and outlining ambient shadow for the given path using a disc
     * light. The shadow may be cached, depending on the path type and canvas matrix. If the
     * matrix is perspective or the path is volatile, it will not be cached.
     *
     * @param canvas  The canvas on which to draw the shadows.
     * @param path  The occluder used to generate the shadows.
     * @param zPlaneParams  Values for the plane function which returns the Z offset of the
     * occluder from the canvas based on local x and y values (the current matrix is not applied).
     * @param lightPos  Generally, the 3D position of the light relative to the canvas plane.
     * If kDirectionalLight_ShadowFlag is set, this specifies a vector pointing
     * towards the light.
     * @param lightRadius  Generally, the radius of the disc light.
     * If DirectionalLight_ShadowFlag is set, this specifies the amount of
     * blur when the occluder is at Z offset == 1. The blur will grow linearly
     * as the Z value increases.
     * @param ambientColor  The color of the ambient shadow.
     * @param spotColor  The color of the spot shadow.
     * @param flags  Options controlling opaque occluder optimizations, shadow appearance,
     * and light position. See SkShadowFlags.
     */
    static void DrawShadow(SkCanvas *canvas, const SkPath &path, const SkPoint3 &zPlaneParams, const SkPoint3 &lightPos,
        SkScalar lightRadius, SkColor ambientColor, SkColor spotColor,
        uint32_t flags = SkShadowFlags::kNone_ShadowFlag);

    /* *
     * Generate bounding box for shadows relative to path. Includes both the ambient and spot
     * shadow bounds.
     *
     * @param ctm  Current transformation matrix to device space.
     * @param path  The occluder used to generate the shadows.
     * @param zPlaneParams  Values for the plane function which returns the Z offset of the
     * occluder from the canvas based on local x and y values (the current matrix is not applied).
     * @param lightPos  Generally, the 3D position of the light relative to the canvas plane.
     * If kDirectionalLight_ShadowFlag is set, this specifies a vector pointing
     * towards the light.
     * @param lightRadius  Generally, the radius of the disc light.
     * If DirectionalLight_ShadowFlag is set, this specifies the amount of
     * blur when the occluder is at Z offset == 1. The blur will grow linearly
     * as the Z value increases.
     * @param flags  Options controlling opaque occluder optimizations, shadow appearance,
     * and light position. See SkShadowFlags.
     * @param bounds Return value for shadow bounding box.
     * @return Returns true if successful, false otherwise.
     */
    static bool GetLocalBounds(const SkMatrix &ctm, const SkPath &path, const SkPoint3 &zPlaneParams,
        const SkPoint3 &lightPos, SkScalar lightRadius, uint32_t flags, SkRect *bounds);

    /* *
     * Helper routine to compute color values for one-pass tonal alpha.
     *
     * @param inAmbientColor  Original ambient color
     * @param inSpotColor  Original spot color
     * @param outAmbientColor  Modified ambient color
     * @param outSpotColor  Modified spot color
     */
    static void ComputeTonalColors(SkColor inAmbientColor, SkColor inSpotColor, SkColor *outAmbientColor,
        SkColor *outSpotColor);
};

#endif
